C.2.8 The Make Macro MAKEFLAGS

Posix requires make to use MAKEFLAGS to affect the
current and recursive invocations of make, but allows implementations
several formats for the variable. It is tricky to parse
$MAKEFLAGS to determine whether -s for silent execution
or -k for continued execution are in effect. For example, you
cannot assume that the first space-separated word in $MAKEFLAGS
contains single-letter options, since in the Cygwin version of
GNU make it is either --unix or
--win32 with the second word containing single-letter options.